In 238 BC on the coast of north Africa a great military general named Hamilcar had just lost a war to Rome over the territory of the island of Sicily and he
prepares to go to Spain.He had a young son named Hannibal and Livy describes the scene:

"Hannibal, then about 9 years old, was childishly teasing his father to take
him to Spain with him. His father still angry at the loss to Rome led him to the
altar and made him swear to be the enemy of Rome as soon as he was able."

-Livy

Hamilcar did bring his son Hannibal to Spain with him and taught him military
strategy. Hamilcar died in battle 9 years later in 229 BC. In 219 BC (20 years
after his oath) Hannibal fulfilled what he swore and became the greatest enemy
Rome had ever faced.